Sorry, but K-Meleon has a little to satisfy you here.
Its GUI is completely different from Firefox one. So interface-related FF-extensions cannot be adapted for KM as rule.
Also we have no visual tool to edit toolbars - just config files.
And sadly there is no universal answer about KM-extensions: as the folder structure of browser was changed between 1.7 and 74 branches, some extensions had lost compatibility with new version (as installation process was simply unpacking files in corresponding folders).
So there are many 'types' of KM-extensions by content (
I wrote about this a little).
Some simple extensions, containing only macros [and 3rd party tools, integrated by macros] work in KM74-75 the same way as in old builds. So they could be used as is (taken from
KM Extensions Central, for example).
But others need some manual adaptation in folder structure of extension and manifest files. Some of them now are one by one replaced by native FF-xpi extensions, with an interface adaptation (button or menu item) taken from the corresponding old KM-extension (we speak about macros).