is it possible to see previous quoted price to particular customer while preparing a quote?
only possible with server edition/cloud edition using web browser multiple tab.
For Desktop edition you have to check the previous quotations one by one before preparing a new quote.
alternatively you can save the previous sales quote as pdf then open with pdf viewer. so you can see previous saved as pdf quotation and preparing new sales quote at the same time.
You can open another window in the desktop edition and browse through the previous quotes/invoices - at least in Windows you can using a right click on a tab, for example, which opens a new browser window where you can navigate to whatever you want
Search the forum. Instructions for opening multiple windows have been provided several times.