There is a way of doing this, which is insanely unintuitive and might sometimes not work
for pcblib → in the schematics editor (KiCad 8) assign footprints → manage footprint libs → there is a folder Icon, from which you can choose altium designer category.
for schlib → in the schematics editor (Kicad 8) you go preference → manage symbol libraries → then the folder icon → select the schlib file type
Note that you can also skip the editor steps by starting from the main KiCad application (with the project files) and go to Preferences > Manage Symbol / Manage Footprint Libraries.
I personally find it counter-intuitive that you have to pick the footprint library type using the little drop-down arrow before opening the folder window, when you don’t have to do that for the schematic symbol library. (I’m surprised you had to manually set the type to schlib, it seems to “just work” for me on Mac w/ KiCad v8.0.8.)
EDIT: In the process of starting an issue, I realized that there probably are some platform-specific considerations for the footprint side since the “selection” is sometimes a directory and sometimes a single file. So while it is awkward, I’m pretty sure it is intentional/necessary.
Thank you very much for the answer, and yes you can totally skip the editor steps, what I found confusing is that the option to import schlib is not present if you try and import a symbol library without going through the library manager.
I think I’m misunderstanding you. Can you go into more detail how you expected this to work?
From my point of view, KiCad has a reasonable separation of tools. In my experience, libraries are not added/deleted often and the decision to do so must be very intentional. It seems reasonable to me to open a unique dialog for the task. Under the hood, the Library Managers are editing “library table” files that are maintained for the user (the Global libraries) and the project (the Project libraries). My understanding (not a dev) is this behavior is partly for legacy reasons and also to make it easy for larger organizations to ensure their designers are always using the most recent libraries / merge changes across updates.