If you haven’t already figured it out by yourself:
I think that the error with regard to panel_cutter’s “Missing manifest…” is due to an issue with the structure of the ZIP file. It should be formatted as follows:
add-on-panel-cutter-v1.0.3.zip
If it contains at least the files
ini.py and
blender_manifest.py
you should be good, assuming you provided the appropriate information for the “blender_manifest.py”.
(The file init.py has 2 underscores on each side of init, which the forum’s software drops.).
If you are intersted in more elaborated information on this matter, please look at the thread