When selecting multiple documents in DTTG, there doesn’t seem to be a way to select everything. This looks like fundamental but missed feature. Or am I missing something?
No there currently isn’t a select all in DEVONthink To Go.
Thanks for the clarification. Can I make this as a feature request then? Is it something you might add in?
You’re welcome.
It’s on our list but I can’t make any promises about an IF or WHEN.
No problem 
I know this’s been always the policy.
There is a new mechanism in iOS that allows a bit easier selection of multiple items. It may be sufficient. Stay tuned for the next release.
I’m guessing this is about the swiping gesture. But it’s not been enough for me for bulk actions.
Two-fingered swiping, yes.