Absolutely, it is technically possible to merge both Bootstraps together. However, it is not recommended as it may lead to a messy and hard to maintain codebase with conflicts between the two frameworks. Despite the challenges, merging them is achievable with just a few additional imports of the new Bootstrap.
Instead of combining different Bootstraps, I suggest exploring alternative solutions:
If your project is small, consider transitioning entirely to the new Bootstrap and abandoning the old one.
For larger projects, you could implement the new Bootstrap in new sections while keeping the old views unaffected by the change. Subsequently, you can gradually update each old view utilizing the new Bootstrap when time and resources permit. The key is to avoid using both versions simultaneously on the same page and instead transition to the new Bootstrap selectively.
Best of luck!