In no particular order

Change 'add walls' to just toggle between a wall and a blank. So if I click a blank it turns into a wall click a wall it turns into a blank.

Reduce the number of geek points required for initial gold OR increase the geek points required when changing the gold value of a creep. If I can make the first creep 1hp and give 10000 gold - there is no point in the initial gold limit. Same for lives if you give away a load of points at the start with easy creeps.

Add 'checkboxes' next to each level you make. At the bottom add 'duplicate checked'. I.E. I build out 10 levels - check 6 of them - click duplicate I now have 10 + the 6 levels I checked.

Add 'increase hp 10%' of checked and 'decrease hp 10%' of checked. etc. etc.

At the bottom of the levels list - have totals for complete hitpoints of your levels, total amount of gold and total point value. I like to try and work out if the map is possible to beat mathematically and keep that quite tight.

I agree with all of your ideas, bt when you say level do you mean a wave or an entire map?

A wave (a level)

i like those first 3 ideas!

but your last idea is a feature for very few creators... not worth the effort to write that, probably.

the increase-hp-idea i'm not that sure either as hps are nor that easily calculated... try and error, testing, testing, testing.
after some maps you get a feeling for the balance between all those kind of values, and have to test less times. further, some map designs change everything...

I had a similar comment in another thread about the dichotomy between providing gold up front versus providing a wealthy creep as the first level... so I agree with that.

I think alchemist's last idea would be interesting; I agree that not everyone would do a mathematical analysis, but it also seems like it would be straightforward to code (# of creeps * # of hit points, sum that, etc.)

The math idea is just a rough indicator - but maybe it would help people and should be easy to do I think?

Another idea ....

In the map editor screen - have a 'pathfinder' button. What this does is changes the background of the map in the editor screen 'pastel green' for a valid path / places creeps could go and 'pastel red' for an invalid path. So you can quickly check if you made a gap too small or to big without having to run the map. Click pathfinder a second time and it goes back to yellow.
I don't know how easy that is - I guess you may need to run the map in the proper runtime code to validate the paths? just an idea