Let's say I'm adding something like citizen to MultiTerm. At the moment, I have to Add New (which is fine) but then it gets un-intuitive. Rather than automatically opening the Source field for adding, I'm in some intermediate stage and have to manually click on that triangle and then Term. When I hit Enter, it just closes that field. The the same for Target, which gets really annoying if you have an inflecting target, in my case, I end up doing that dance 4 times because I need singular, plural, and genitive for both. That's a lot of time spent clicking and that triangle is so small I often mis-click.
The intuitive and time-saving path would be this:
On Add New, automatically open the first Source field for editing. On hitting Enter, automatically close the current field and open a new field for editing. If I hit Enter again without having added a second Source item, automatically jump to Target and open the first field for editing. On hitting Enter, close and open a new field for editing. On hitting Enter in an empty Target field, save entry and leave editing mode. Cancel operation at this stage is much less common and can be carried out via the toolbar or shortcut key.
This would save a lot of clicking and having to jump between mouse and keyboard.
It sounds like you are using an older layout or version of MultiTerm. With MultiTerm 2017 we have introduced a new layout that works in exactly the described manner, i.e. you click Add New and are immediately placed in the text input box for the source language.