For getting multiple animations into a glTF file, I have been exporting an fbx from maya using the game exporter, that splits the animations up into a single file.

Then I use the following FBX to glTF tool.
https://github.com/facebookincubator/FBX2glTF/releases
This outputs a glTF file which, when loaded using the ThreeJS glTF importer, gives an array of animations that you can use the AnimationMixer to control playing/pausing/blending animations in.