@Void, @Crowborn and others having the issue of not seeing anything in the distribution tab, make sure youve got a updated IWBMS on steam like @russafiii mentioned and then it should be working properly. Ill update OP to include a little note concerning this.
@thiosk Indeed the distribution panel isnt well suited for bulk insertion operations like that atm.
Ideally id like to fix up the entire distibution panel a bit at some point in the near future so the points youve raised work better allong with some more drag and drop improvements.
However when doing amounts 250 items this may still result in quite some dragging, depending on how they need to be distributed in the list lua might be a valid option as well.
Ive played around with creating a little helper script for that purpose and came up with the following which may be helpful to you:
The top part has some settings you can modify, the way it works would be to have all the items that you wanna add in bulk to the distribution in a seperate module wich will act as a category.
You can set a default spawn chance and add target containers, the nested containers need to be seperated with dots as per example and be aware that the container names are case sensitive.
When running the script it will add all the items from the defined module to the targetcontainers, afterwards you can optionally use the right side item filter box to filter on the module name (see img) instead of item name incase you need to override some default spawn chances of some of the items.
Additionally ive also created helper script to remove items from the distributions in bulk, it has somewhat similar settings in the top part:
Hope this is usefull, both scripts adjust to the mode youre running the program in (mod or dev), in mod mode the remove script for example will not touch and base game entries.
Also, if there might be need for other similar scripts feel free to post a request in this thread!