Creating a slot based inventory system with items different tabs

I would like to create an inventory system. Below are some screenshots of what the design looks like, which should help provide a good idea of what I would like to implement. (And also please note that the background in these photos is not from something I have created. It is a backdrop from the game “The Long Dark”. I use this when creating UI.) .

First, I have the utility belt. (Look at the very top of the image.) . When you collect an item, it will go into the slot that is the closest slot to the left, and that it is available (ie:not full with another item):

Then I have the actual backpack or inventory system. This design separates the items into different categories. Right now in the picture you are on the aid category and all your food and other aid will display in your 9 slots available. However, if you were to click on tools, all the tool information would be saved and only the tools items will be displayed and so on. When you can’t carry anymore tools in each slot than you can’t carry any more tools. However, if for example you have available slots in the aid category than you can still collect items there. Below is an example of what I would like the inventory to look like. Notice how some items can stack and some items can’t, and when they reach their limit you can’t carry anymore of that item and when you collect something it is moved onto the next slot. Also, to the left is some information about the selected item:

If it’s not too much, I would love a breakdown on how I would do this. I have watched several videos but I think my inventory is too different to adapt for some of the setups I’ve seen. Most notably the fact that the items are broken down into different categories. I have tried to make this myself, however I think I have a habit of overcomplicating scripting to such an extent that when I debug it’s almost impossible to do. Also the performance is impacted greatly with the current inventory I have. However I think creating flawless systems comes with a lot of practise and experience. I am very serious about this project which is why I’m ready to completely redo this system since I know there is a better option than what I am doing. Any help would be appreciated. Thanks!