I've got two options you may wish to consider, marcel6.
You may utilize the QuickBooks Online Desktop app, which lets you stay logged in for an unlimited period. You can download it to the following link: Get QuickBooks Mac & Windows Apps, powered by QuickBooks Online.
Also, you can adjust the time required to be signed out for inactivity in QBO. Here's how:
For further insights into this, please check out this article: Change the timeout duration in QuickBooks Online
I'll be here to lend you a helping hand if you have other concerns.