Toolbar not big enough? Tired of searching through 100 items for the same few you need? Try Hot Swap. This fully configurable mod allows you to quickly change what item you have selected when you need it the most.
Now items like belts, power poles, train stuff, capsules, only need to take 1 hotbar slot (if any) then you can quickly rotate between them. This mod was inspired because I was really tired of finding/clicking locomotives and cargo wagons, as I rarely have them on my hotbar and wanted to find a faster way to swap between them once I did have them selected.
Just quickly add items in your "Hot Swap" list, and you can use a custom keybind (CTRL+Mouse wheel up/down by default) to quickly jump from item to item. Useful when you want to switch between similar items that you don't frequently use. Also has fallback support so if you run out of 1 item it will revert to the previous one in your list again saving you precious seconds.
You can now link sets of swaps together, allowing for you to quickly jump between similar sets. By clicking the link icon on one or more sets, it will link that set (row) with the one below it. When using the set swap hotkey (ALT+Mouse wheel up/down by default) it will swap you to the Nth item of the next/previous set, where N = the same number column. For example, take a look at the 2nd image in this mod. You can see the belt rows 1 and 2 icons are linked. That means the yellow belt, red belt, and blue belt sets are all linked together. If I have a yellow splitter in my hand, and Row Swap up, it will swap me to the red splitter as they are in the same column.