If your UIM tools are attached to worksheets or plots they should work pretty much the same as in Origin 5. However, floating UIM tools have not worked since Origin 6.0 and you'll have to rebuild those as DialogBuilder dialogs.
You can use Origin 5's Uimedit.opj in Origin 7, but it's not as useful due to lack of floating tool support. However, the UIM toolbar still works.
DialogBuilder tools are much more versatile and easier to work with than the old UIM tools. It might take you a while to get used to DB, but I think you'll like it in the end. However, you need MS Visual C++ or something comparable to create DialogBuilder tools.
Thanks for the quick answer. But finally it's not a question of the better way of programming floating tools. It took a lot of time to develop our Dialog Interfaces and we just want to use them and we don't want to rebuild them. It's frustrating that we still have to use the old Origin5 Version, cause Orginlab is not able to produce a compatible new Version of its own Software.