I always Authorize RD trough ResolveURL from manage dependencies the same way as you mentioned above, done this in Kodi 19.4 v7 from RAI, and 19.4 v8 the one you can download directly from their website. I authorize RD once, and I didn’t have to authorize RD in each add-ons.
But few days ago I installed and tested the New Kodi v20 Nexus “Alpha version”. I tried to authorize RD from Manage dependencies> But ResolveURL wasn’t there, and according to developers This will not be available in this version of Kodi.
They left it to Kodi Add-ons developers to integrated in their add-ons only.
Maybe they meant that it will not be available in the Alpha version only. But I’m not sure.