Can't merge two partitions?

[jh.dks]

Hey all! I decided I want to bring some life back to an old MacBook.
It stopped using it running ML but apparently I did upgrade it to Yosemite at some point. It has a small SSD and used about 50 GB of it. I made a new partition with the remaining free space to run Mojave (which it technically doens't support, but it's running absolutely great).

After deleting some unnecessary files on Yosemite, I noticed it was down to 30 GB so 20 GB free space. I wanted to quickly make a new partition to check out how it'd run Catalina, but I can only make new partitions from the free space available on the 2 exisiting partitons. And I can't merge those. Also only possible with Disk Utility in Mojave or the Catalina installer, because in Yosemite everything's just greyed out.

I'm not the smartest with these kinds of things, but they are logical volumes and I did some stuff in Terminal (don't ask me what, though), and now Yosemite would let me delete the Mojave partition, but that's it. Any fix for me?

Long story short:
I have 1 SSD with 2 partitions:

• 50 GB "ADMIN" (30 GB used, 20 GB free space) - Yosemite
• 65 GB "Macintosh HD" (40 GB used, 25 GB free space) - Mojave

I can have turn the 20 GB and 25 GB of free space into 2 partitions, but not into one. I also can't give the 20 GB of free space from Yosemite to the Mojave partition.
I wouldn't really want to loose the Yosemite partition. I don't care about Mojave: it's a fresh install with just a lot of junk already installed I was planning on using with this computer.

Really appreciate your input!! Thank you!!

 

[Fishrrman]

Can't really understand "where you want to be" when done.
Do you want one partition or two?
Which one of the OS's do you want on it?

 

[Brian33]

I think the OP wants to combine the 20 GB free space in the ADMIN partition (Yosemite) with the 25 GB free space in the Macintosh HD partition (Mojave) to form a third partition (~45 GB) on which he could install Catalina. Is that right?

The OP has noticed that the free spaces can be turned into new partitions, but those new partitions cannot be combined -- probably because they are not adjacent on the disk.

If I'm correct about his goal, I think he'd have to delete the Macintosh HD (Mojave) partition, make the free space in the ADMIN partition (Yosemite) into a new partition, which (I think) could be combined with the remainder of the disk, then create a new partition for Mojave, leaving space for a third partition for Catalina.

 

[Fishrrman]

I think the OP's best course of action would be to:
- back up existing partitions to an external [partitioned] drive using either CarbonCopyCloner or SuperDuper
- ERASE the internal drive
- RE-partition the internal drive to the desired configuration
- Restore to the newly-created partitions.

This might be the ONLY "course of action"...

 

[jh.dks]

Can't really understand "where you want to be" when done.

I'm sorry, I'm not the best at explaining this, especially not in English.
I want to keep the Yosemite partition, but not use it. Then I want to use the remaining free space for Mojave.
But just for giggles I wanted to combine the free space from both partitions to run Catalina to see how it'd run. I haven't upgraded my daily driver to Catalina (because I still use some 32 bit apps), but my new laptop came with it and for what I want to use it, Catalina might be the better option... But the end goal is two partitions, of which one is being used daily.

I think the OP wants to combine the 20 GB free space in the ADMIN partition (Yosemite) with the 25 GB free space in the Macintosh HD partition (Mojave) to form a third partition (~45 GB) on which he could install Catalina. Is that right?

Ding, ding, ding!!! That's what I wanted to try for fun.
In the end I'd just like to have two partitions and merge the 20 GB of free space with the Mojave partition. I don't really need a lot of space, it's no big deal, but it's also kinda stupid it's assigned to a partition where I'm not really gonna use it.

This might be the ONLY "course of action"...

Ouch, that sucks. I read something about 'logical storage' being impossible to resize and merge and what not, and you could revert it back to whatever it used to be. Obviously Disk Utility did something to this drive when I partitioned it. But unfortunately it's beyond my knowledge and skills to understand what's going on and how to fix that with the Terminal commands I found online...
Disk Utility in Mojave and Catalina also give me very other options compared to Yosemite...

Thank you all for your input so far!!!

 

[Fishrrman]

"I want to keep the Yosemite partition, but not use it. Then I want to use the remaining free space for Mojave.
But just for giggles I wanted to combine the free space from both partitions to run Catalina to see how it'd run."

OK, my advice:

First, FORGET about Catalina unless you are committed to upgrading to it.
If you want to fool with it, get an EXTERNAL SSD, and install Catalina onto that.
Don't mix Catalina on a drive with an earlier OS that you depend upon.
This forum is filled with users who wanted to try Catalina "for giggles" -- and then were sorry that they did.

Next, if you want Yosemite "around", but will not be using it, DON'T WASTE DISK SPACE for that on your main drive.
Again, get an EXTERNAL drive (doesn't have to be an SSD), and use either CarbonCopyCloner or SuperDuper to "clone over" the Yosemite partition to that drive.
It will be bootable "if you need it".
But it won't be clogging up your main drive.

Having said that...
Since Mojave is the only OS you really seem to want to use on a day-to-day basis, I suggest you have only ONE partition on the main drive, for Mojave.

 

[jh.dks]

First, FORGET about Catalina unless you are committed to upgrading to it.
If you want to fool with it, get an EXTERNAL SSD, and install Catalina onto that.

Thanks for your advice! To be honest, I'd probably want to run the most recent version of macOS it can handle, I was just afraid I might need to use some 32 bit apps on this machine every now and then, but I probably don't need to.
It doesn't support Catalina, though, but I was able to install it to see how it'd run and honestly... it runs great. Literally the same as Mojave.

I got an external HDD so I can back up my Yosemite stuff. Thanks everyone!