Ah, no I hadn't seen that. By the title of "storage categories" I did not anticipate that might have anything to do with capacity.

We are currently (manually) allocating based on volume (cubic metres) however that does not appear to be an option even though it is a dimension on the product template.

Hmm, it appears to me that it is that only triggered on a put away rule. Is that right?
If so, it is not an adequate solution as it will not prevent an internal transfer breaking the capacity rule.

You have Internal Transfers being created by people before they are moving things around?

Receiving is a 2 step process. We bring goods in often in a larger container. We then break them open and then transfer them into their locations.
Sometime we may need to relocate stock based on its popularity to ensure they are closest to the shipping area. We need to ensure that those locations are not over allocated.

We also want to know how much free capacity is available so that we can top it up from the bulk stock area.