I can't do anything about the search function, but I can tell you that those bonus tiles are IMPOSSIBLE to mod. I really wish they were, but no matter how much I complain the devs will not (maybe just cannot) make them moddable!

Modding bonus tiles takes a bit of time and effort, but it spoils the game in the long run. But if you are really interested all you need is a hex editor, hex edit was the one I used to use.

Anyway s

step1  is to start a new game

step 2 save the game with something memorable

step 3 open the save file using hex edit

step 4 look for the following patterns after the name of the planet in the decimal side of the hex editor. BTW you need to change the font of the hex editor to make it more legible:

00 00 00 00 01 00 00 00 00 00 00 00 40 00 00 ........100 research

00 00 00 00 02 00 00 00 00 00 00 00 40 00 00 ........100 food

00 00 00 00 03 00 00 00 00 00 00 00 40 00 00 ........100 industry

00 00 00 00 04 00 00 00 00 00 00 00 40 00 00 ........100 approval

00 00 00 00 05 00 00 00 00 00 00 00 40 00 00 ........100 influence

00 00 00 00 06 00 00 00 00 00 00 80 40 00 00 ........300 research

00 00 00 00 07 00 00 00 00 00 00 80 40 00 00 ........300 food

00 00 00 00 08 00 00 00 00 00 00 80 40 00 00 ........300 industry

00 00 00 00 09 00 00 00 00 00 00 00 41 00 00 ........precursor library

00 00 00 00 0A 00 00 00 00 00 00 00 41 00 00 ........precursor mine

step 5 save the file

step 6 become extremely badass and take over the galaxy

The trick is to look for the patterns, pick a world with a few bonuses and then seek that world in the hex editor, then look for patterns arranged like above and then adjust them. The above rules are from back in dark avatar times and were slightly different from GC2 style, but it was in the same format with the 01 - 0A and the 80 40 and so on, the difference was with the spacings. Its essentially going to be a bit of trial and error, but eventually you are going to have worlds with 10 precursor mines and 10 libraries and more approval than you can wave a big stick at.

On  a serious note: these type of mods will not be eligible in metaverse games.

There is some more information in "get the bonuses you've always wanted" a thread I did a long time ago.

Enjoy

Is it possible to actually create new kinds of bonus tiles with hex edit (I don't think it would be, but I hope I'm wrong...)

I'm fairly certain that it is impossible too. All hex edit does is change the saved game files. You would need to be pulling open the hood and tweaking the engine itself. In all likelihood you could possibly do it, but it all depends on how much moddability we're allowed. So far its mostly surface changes, planets and values and attribs. What you're asking for is too techie for me to answer.

What other bonuses would you need?

I've always wanted to create a set of economic bonus tiles, as well as 300% and 700% tiles for influence and morale. Maybe something for soldiering or logistics or whatnot... I don't really know beyond the first few, but I would definately want more to add some variety to the game.