Garry's Mod Spawnlist Generator
Normally, you can click and drag the items between spawnlists. However, if I move an item away from one of the default spawnlists (e.g. "Construction Props", "Comic Props", "Builder/Basic", etc.), it is no longer in that one, and I like the default spawnlists to stay as they are (call it OCD if you want). (AFAIK, you can't duplicate a spawnlist entry in-game.) Also, for some reason, they didn't use valid JSON for the spawnlist format, even though I think they easily could've. Instead, it's a weird form of JSON with no colons and varying spacing.
Usage: Create a new spawnlist. Go to GMODGAMEDIR\garrysmod\settings\spawnlist and note down the name and ID number (filename should be like ID-Name.txt). For each item you want, locate it in its original spawnlist, right-click it, click "Copy", and paste it below on a new line. To add things other than models, use the scheme below:
FILENAME:MyName[Required] Filename of the spawnlist. May include spaces, but no special characters (e.g.:). Will be used for filename.DISPNAME:MyNameDisplay name of the spawnlist. May include spaces and special characters. If you want a name with special characters, put it here and put the same name in NAME with all of the special characters replaced with underscores (_).ID:theID[Required] 3-digit ID. Must be between000and999and ideally the next consecutive ID (follow above instructions).ICON:theIconIcon for the spawnlist.HEADER:theHeaderA section header in the spawnlist. May be placed anywhere in the list. You can have multiple.
Convert it to a spawnlist here. Then, download the file and put it in the directory you got the original spawnlist file from, replacing it. Go to one of the default spawnlists, move an item, and click the green Revert arrow. Your spawnlist should now contain all the items you entered.
If you need help locating your Garry's Mod game directory (GMODGAMEDIR), click here (opens in new tab).