Onetab is recommended by Firefox, so it gets monitored for security in some form, but regarding privacy it sends your visited domains to google to get the favicons but the rest of the privacy policy seems very good. As with any proprietary software, you can not really know if it is safe, you just have to trust it. As an alternative I would recommend Tab Stash, it does the trick for me

Have you considered using the bookmarks tab (ctrl + b) and creating a series of folders to organize your work ?

Here’s how i do it. I made several folders of topics with subfolders of sub topics for relevant websites for each topic. So for instance, you’d have cooking as a topic and then main dishes as a sub topic and desserts as another sub topic.

When working on a project, I’d make the topmost folder for projects and within it Projectname. Whenever i want to work on that project, i click ctrl + B, right click on the sub project folder and then click on “open all tabs”. Voila, similar functions using the native commands.

Once your project is done, create a folder and move it to the bottom, name it Archives and drop your old projects there.

You can even have a R&R folder, where you put all the tabs you usually open when you’re just navigating for leisure. Or an Organization and Planning folder, where it opens all your email accounts and your calendar app of choice, as well as your organization software like Notion, or Jira or so if you use it to have a workspace to organize stuff before getting to work, so you can best address your emails with either calendar blocking or just scheduling and writing notes.

I also suggest backing up all your favorites regularly through export into your hard drive and later into an offline drive. That way, if your pc breaks, you can just keep going on a new pc. Or you can use firefox account and sync it.

Feel free to create workspace folders as you see fit for your organization workflow.

I also have a shopping folder where i add things I’m thinking of buying so i don’t fall into the trap of impulse buying. Or things i might need to buy if something is about to fail, like an old phone or boiler or just clothes i like.