If this button exists:
Go /quickaccess FOLDERCONTENT
then there is a delay caused whenever you click the "+" symbol at the end of the tab bar.
It's not a huge delay (1 or 2 seconds).
I doubt I'll use this button, so I don't really care -- just letting you guys know.
Is that with the listing at the top-level, or in a sub-menu?
If it's at the top-level, the listing will be rebuilt quite frequently (including every time you open a new tab).
That's not ideal, but also should not be that slow (and isn't here).
There must be something in your Quick Access list which is slow to enumerate or to get the icon and name of. Maybe something pointing to a network share which is slow or not accessible.