For browsing help files, the Dash application is very useful on Mac and iOS.
Here you can click to launch Dash and install our plugin help:
MBS Xojo Plugin and MBS FileMaker Plugin
You can download the archives manually on our website:
FileMaker and Xojo (Real Studio).
You can also add Xojo documentation itself to your dash set, see download in preferences dialog.
For FileMaker you find the docsets for v15 and v16 here: FileMaker Dash Docsets
Feedback is welcome.