To open another window in the App, using the + sign, is there a way to do this using the + sign, without the App crashing? It was able to do this in the past.

Hi there info1545,

Using QuickBooks Online in multiple tabs is a great way to enter your information based on prior entries as well as compare various information within your books. I can assist you with getting this back up and running.

One thing that can be affecting your navigation in the app is cache. These temporary files can cause errors like the one you're experiencing, so here are a few steps to take in order to resolve any issues caused by app data:

• Clear the app cache if you're using the QuickBooks Online app for Windows or Mac
• Try a browser if you're using the app
• Try a private browser window
• Try another browser type
• Make sure you're using a supported browser and system
• Reset your Internet or try on another computer or device
• Try deleting the app and installing it once again

If the error still persists, I recommend contacting our support team outside of the Community. They'll be able to assist you with further troubleshooting and give you the next steps to take. You can reach them using one of the following methods:

Phone: Call us at 1-855-253-1536 from Monday to Friday between the hours of 9 AM and 8 PM EST.
Schedule a Callback or start a Chat: click (?)Help in the upper right > type and enter "Contact support" into the QB Assistant > click Contact Us > explain your situation > click Let's Talk > choose Get a callback or Start a Chat. 
Social Media: Facebook, Twitter, and Instagram.

I hope these steps are able to get you back to working in QuickBooks Online with multiple tabs. If you need some more information feel free to reach out here. I've got your back!