Do i add a new item to as I’m currently running both? What might happen in the future?
It’s unclear what you’re trying to do, additional details would be useful. Thanks.
I think I’m testing DT3 and letting it access the DT2 database. Now when I clip a new item it goes only to DT3 when it’s running. Since I’m unsure as to whether I’ll be updating I’d like to have everything merged. Does this make sense?
If you’re using the same databases (extension .dtBase2) in both versions, then the items should be available in both versions. The only exception is the global inbox, by default DEVONthink 3 uses its own.
version 3 (properties) says
DEVONthink 2.dtBase2
Version 2 only shows the location (different) and not the database name
Which edition of DEVONthink 2 did you use?
2.11.3
DEVONthink Personal or DEVONthink Pro (Office)?
Personal
In this case the databases aren’t the same ones, DEVONthink 3 uses its own copy. I would recommend to use only one version but in case that you need both the only option would be to synchronize the databases (see Preferences > Sync).
Might syncing not cause more problems than it solves? If not what are the steps to get the two in sync?
Synchronizing doesn’t cause any issues, e.g. it’s also used to synchronize multiple computers or iPads/iPhones. However, as version 3 is still a beta and as version 2 (especially the Personal edition) doesn’t support all the extensions of version 2 (e.g. custom metadata or reminders), I would highly recommend to use only one version concurrently.
Trying to sync DT3 into DT2. If I’m proceeding correctly I’m being asked for a password.
Are you trying to sync DEVONthink Personal 2.11.3 to a database in DEVONthink 3?
If so, while this is technically possible, I would not advise it.
- If you need to use Personal for actual daily work, then continue using it.
- If you want to beta test and report on DEVONthink 3, separate the two apps in your mind.
What’s happening is that while testing DT3 I’ve not been careful about what I put in 3 and what I put in 2. Just attempting to unconfuse myself.
You can create smart groups - see Data > New > Smart Group - in DEVONthink 2 or 3 with criteria like this…
Obviously using whatever interval you desire for the Date Added.
Just tried it. Is there an additional step necessary or is the created smart group located somewhere?
No, there’s no additional step. What did you have selected when you created it?
I mirrored your example exactly.
I didn’t say what I had selected, so exactly would be impossible 
The smart group is either in the database itself or in the Smart Groups section of the sidebar.