this is an old annoyance I've encountered from OOo era which persists in current LibO releases and master branch (last tested on tonight 4.0.0.0 daily build)

when you are in the process of assigning a macro to a custom toolbar button LibO freezes for 2 seconds.

Tools --> Customize -> Toolbars --> Add --> My Macros 

I notice a transitory freeze of 2 seconds before the "My Macros" will expand.

you can only appreciate this if you have a long list of macros (I have more than 100) and you are on a slow computer (the test has been done on a 5 years old laptop)

it's a minor annoyance I know, but there's probably some sill underlying performance issue to do such a simple action