Does BUSY support e-way bills for exempted goods or non-taxable supplies?How do I generate an e-invoice in BUSY?

No, you are not required to generate eway bill for exempted items or non- taxable supplies.
To configure e-invoice from BUSY need to follow given steps
Step 1:Go to administration menu and then select configuration from it.
Step 2:Then select feature and option and then click on GST/VAT option.
Step 3:Then search for e-invoice required option and mention Y in it and then click on configuration button to configure it.
Step 4:Mention all necessary details in configuration field like from place and pincode and make sure to save the configuration.
Step 5:Open your browser and Log in to the e-invoice portal.
Step 6:From the main menu, select API registration.
Step 7:Click on the Create API User tab under User Credentials in the API registration menu.
Step 8:A taxpayer will receive an OTP on the registered mobile number. On entering the OTP, the API registration form will open. 
Step 9:In the API registration form, select through GSP to integrate the APIs through GSP. 
Step 10:Then select the GSP name from the drop-down list i.e webtel electrosoft pvt ltd and create the username and password for it and click submit.
Step 11: Repeat the step 10 for creating the GSP user name and password for pinnacle finserv advisors private limited.
Step 12: Mention the GSP credentials in the BUSY GST/VAT configuration and make sure to click on save button.
Step 13: Go to administration menu and select configuration from it.
Step 14: Then select voucher series configuration and then select the relevant voucher and then click on voucher configuration button.
Step 15: Then navigate to input transport details, generate e-invoice after saving option and mention Y in it and click on save button to save the configuration.
Step 16: Modify the voucher for which you want to generate the e-invoice bill and resave it, BUSY will ask you do you want to geneate the e-invoice yes or no. click yes and geneate it.
Note: If you have already created the GSP credentials for e-way bill then you do not required to create GSP for e-invoice portal separtely.