I’m not sure what the Mac has for automation tools, but if you can simply set up some sort of automation tool so that if you press a particular key combination that is not used for anything else in Blender, you could implement basically the solution I mentioned in my previous post: press a special keyboard combination, then make the mouse go to a particular location relative to the Blender application and click. Then you can immediately type your new current frame number.
In the past, I’ve forked the Blender code base and have implemented changes in the main application. I believe that’s probably the only way to realistically implement this feature. If you’re not an experienced developer (or if you have no desire to become an experienced developer) I would not recommend digging into Blender’s code base, though.
While you can do a LOT with writing Blender add-ons, I don’t believe this feature would be easily implementable because you will run into multiple problems:
If you want the cursor to jump directly to the frame number control in the application (as my workaround above does), first you’ll have to make sure that every workspace has a tImeline pane (though not necessarily in the same location like my workaround above). However, I’m not aware of a way via Python to jump directly to a particular text/numeric control and basically click on it so that you can start typing. If there is a way to do this, I would love to hear how to do it. But in my experience with coding Blender add-ons, this is not something that is possible.
An alternate implementation would be to have a pop-up box appear with the text box already in focus so that you can start typing. After hitting Enter, the frame number would change. Unfortunately, I’m not aware of an easy way to create a new pop-up with an instantly-typeable textbox via Python in Blender. MAYBE there is a way to call some external Python library that will show the pop-up – or a separate program, which would then return the new frame number…but that seemed like too much work so I didn’t pursue that angle.
Anyway, unless someone submits this idea as a future Blender feature and the devs implement it, IMO your best bet on the Mac is to look into keyboard automation/macro tools for that platform.
Hope this info is helpful, and good luck!