at this moment you cannot create branches using the Administration Tool, you have to use your favorite SVN client to do this task (and the same for merging).
Regarding the handling of branching, I usually configure globally at the server level (Admin Tool > Administration > VCS Management > Configuration) the default URL of the VCS repository (the main code trunk), for example, http://localhost:18080/svn/vdprepo/trunk. Then I create several databases: one main database pointing to the default VCS configuration and more databases for the branches (Admin Tool > Administration > VCS Management > Databases > Configure), for example, http://localhost:18080/svn/vdprepo/branches/vdprepo_b1.
In this way, developers can check out code from a branch to their local virtual database and check-in to the branch using the usual process and if some changes are needed in the trunk is as simple as switch to the main database.
Recommendations about branching? well, this question doesn't have an easy answer because it really depends on your specific project (and maybe this is more a SVN question than a Denodo question, but it is a good question in any case). In my opinion, in general you should avoid the creation of different branches if they are going to edit the same views.
But, the main point should be: "your trunk has to be guaranteed to be stable all the time". So, in heavy projects, each developer should work on a branch (never in the trunk) and when changes are done and committed, someone (usually the project manager) has to review all the changes and merge them to the trunk. And when the new version is in the trunk, be sure your testing team execute all the appropriate tests!
Hope this helps.