Create a book per job
As there is no limitation on the number of books you can create a new one by easily copying a book with the right chart of accounts, and rename it to the new job. Interesting about this approach is that you can share the book with the customer for example so they are aware of the next bill that is coming up.
Create one book and create accounts per job and group those together
For example: on the incoming side (green) you have the accounts Services_JobA and Services_JobB. On the expense side (red) Transport_jobA, Materials_JobA and Transport_jobB and Materials_JobB. Group these to Expenses_JobA (red) and Expenses_JobB (red) to get total expenses per job. Group incoming and outgoing per job together to Result_jobA (gray) and Result_JobB(gray) to see the results of each Job.
Use Job hashtags (#jobA, #jobB) on your descriptions
Hashtags on bkper are searchable and will give you an instant overview of expenses made per job. You would record transactions like:
02/07 200 ProviderX(yellow) >> Materials(red) #jobB
02/06 160 ProviderX(yellow) >> Materials(red) #jobA