Creating Purchase Quote using AL Code
Yes you can select lines by three dots i just want to make it easy for you to filter these selected lines.
for the vendor selection lookup see the below attachment:
This is a Built in Function on Vendor List Page just use the List page to Lookup the vendors and use this function to get the selected vendors and you may store the string to a Text variable that can be used to filter the vendor record variable while you are generating the PQ.
here is the example how to use the above function:
procedure TestCase()
var
VendorList: Page "Vendor List";
SelectedVendors: Text;
begin
VendorList.LookupMode(true);
if VendorList.RunModal() = Action::LookupOK then
SelectedVendors := VendorList.GetSelectionFilter();
end;
Please mark this answer as varified if this was helpful.