I know it’s not the right time to ask for new features but…
I’m a hardcore heavy user of DevonThink. my Databases have easily 30 GB. For my job I created a database and use tags really intensive. With Ammonite (for those who don’t know it: it’s a fantastic tag visualiser, search tool for DT (https://www.soma-zone.com/Ammonite/) you can easily search for a combination of tags describing document in types, client names, projects, content, proposals, etc. all in a beautiful dynamic rendered word cloud)
When I mentioned a year ago, that this would great to have this within DevonThink, I got a pretty clear: “Thats what we are going todo”. However, in DT3 it’s not there and Ammonite cannot read the correct file names 
This is really a big downer for me. Also where is the straight forward standalone search window (command-f) Searching is much harder for me now… Guess I have to get used to it.
But coming back to my first point: There is this nice word cloud within a document. Isn’t it possible to have something similar on a tag base across all documents?
Did you have a look at the Tags filter, see Tools > Filters > Tags?
Also, please review the built-in Help.
@cgruneberg: Wow --> Thank you so much. This was what I was missing. Fantastic 
Sorry that I didn’t find it.
@Bluefrog:I did; I even bought the new book from Michael Malzahn (but didn’t read yet) and I did spend some time on trying… However: Sometimes the problem is infant of the computer
No worries!
I’d suggest you start with the Documentation > Getting Started chapter.
@BLUEFROG: Great tip…(with Tools-> Filter->Tags ) but how I can combine a selection of some tags? by clicking some of the tags in the tag cloud?
The Tags filter pane is exclusionary, i.e., once you select a Tag only related Tags are displayed. This allows you to fine tune the results by not displaying unrelated Tags.
Thank you very much - a powerful option 
You’re welcome and yes indeed it is. Dont forget the selected Tags appear in the Information Bar above the item list, like so…
The Tag Filter appears in the lower left section of Preview pane, correct? Is there a way to “detach” or move it to a different location, such as a top bar covering the whole screen width? I also can’t seem your screenshot - how do I get to see this view?
Sorry, I didn’t pay attention, the bar “Tag Filter” appears on top of the list - case closed.
No worries!
Doing this I see a list of folders containing tagged documents - but I want to see a list of the tagged documents - how?
Using “find” to look for tagged documents I get a document list …
tried to move tag objects from the tag cloud to the search field - this does not work 
pls help, thanks!
E.g. use the filter for a smart group like the default one “History”.
thanks. in addition, can i do a restricted search within groups/folders? On using smart group “history” I see alle groups/folders …
on editing a smart group I can restrict the search … ist there an easier way?
and … nested searches like this with “find” or “search” (using german version) using AND and OR
tags:Ilse scope:selection {any: tags:StB;EA}
searching like this the “object way” using the tag cloud
Only by editing the smart group or using the advanced search.