I think Pof, which embeds openFrameworks (much like Ofelia did), runs on a different thread (I think). But I have tried closing its window and that crashes Pd. But I could be wrong, as I could be doing this the wrong way.
Switching back to another external that embeds OF, since you have switched from Ofelia to Gem, can be discouraging. I just thought of mentioning that Pof runs on a different thread (I think).

Did you try installing the externals on the second machine through deken, instead of transferring them?

What do you mean by "recompile"? When you install an external object through deken, there's no compilation going on, you're just downloading a pre-compiled binary file (the external object, not its source code) for your architecture (that would be macOS in your case). Are you sure the computer where you transfer your patches and externals has the same architecture as yours? What are the error messages you get?
I don't have a mac and it might be some issue with apple doing all this quarantine stuff, but I could be wrong in this.
Can you post the error messages you get?

Have you tried enabling "Init" in the toggle's parameters? Right-click on it and select properties. In the window that opens, under "Parameters", click the menu and select "Init". Probably you're aware of that and it might not work with abstractions though.

Can't you send 248 to [midiout]? That's the MIDI clock byte. Just setup a [metro] to the desired tempo and connect its outlet to a "248" message. Then use a MIDI interface to send that to your other devices.

@playinmyblues [declare -lib Gem] does what you did by loading Gem from Pd->Preferences->Edit Preferences etc, but only for a specific patch and not every time you launch Pd. If you use Gem a lot, then your approach is probably better, but if you use it in specific patches, then you might want to remove the startup and path stuff in Pd's preferences and just use [declare -lib Gem] in the patches where you use Gem.
As for formatting your messages in this forum, when you want to highlight something inline, use a single ` character (below the tilde character, at the left side of key 1) at the beginning and another one at the end, for example: `[declare -lib Gem]`
If you want to highlight a chunck of code (or a one-liner but separated from the rest of the text), then use three ` characters at the beginning and the end. For example:
```
Put your code (with many lines)
in here
```
and it will be highlighted with a black background.

@kroklop92217 I have no idea. I bought a physical copy years ago, don't know where it's at, at the moment.

I also found this book really helpful when I started developing Pd externals https://books.google.gr/books/about/Designing_Audio_Objects_for_Max_MSP_and.html?id=9yHCvrfxPwUC&redir_esc=y

It seems that the externals-howto tutorial has moved to the GitHub repository. I don't know if you're aware of it, it's here https://github.com/pure-data/externals-howto

It should be in /usr/lib/pd/extra, but as @dreamer wrote, if you [declare -lib Gem] you should be able to use it.