We don't have any ability to customize UIs yet, although we're certainly open to feature requests.
We do have a "Record Page" for each individual record that shows a tabular view of related records from other tables, here's a screenshot from our website: https://mathesar.org/_app/immutable/assets/step-2.CKT9S1j0.a... - you can create new linked records directly there.
We do have a "Record Page" for each individual record that shows a tabular view of related records from other tables, here's a screenshot from our website: https://mathesar.org/_app/immutable/assets/step-2.CKT9S1j0.a... - you can create new linked records directly there.
As for working with multiple linked tables, while editing data, you can search through nested links easily, here's an screenshot illustrating the record selector: https://mathesar.org/_app/immutable/assets/step-3.SKu3rwM2.a...
We also have a visual query builder that can join data across tables: https://github.com/user-attachments/assets/7ff100fe-cd26-422... and https://github.com/user-attachments/assets/0df680d3-621d-466...
I hope that helps!