customise combobox in 'new invoice'

I would like my comboboxes for ‘Client’ and ‘Item’ to be a dropdown list (not editable) only populated from the database. How may I customise the code?

For the client list you can just hide the ‘Add client’ option. For the item lists you’d need to change the input to a selectbox.

Sorry I forgot to mention that I am very new to Laravel. Forgive me but How to I change the input to selectbox and how to I hide the Add client option?

This will require non-trivial code changes, you may want to look into hiring an experienced Laravel\KnockoutJS programmer to help you.

Ì am very optimistic about new challenges. I love the 'non-trivial’part. I just need a simple guide to start from.

I can tell you that most of the changes you’ll need to make will be in this file:

Beyond that you’ll need to figure out from reading the code.