Does anyone know of an application that allows me to edit stl or stp files?
Tinkercad will do it for free but is fairly limited. No automation, only a ruler for feature placement, no easy chamfer function and etc. Having said that, I just imported a part that is meant to hold the tips for a heat insert tool into Tinkercad and had my way with it.
You have to do things in a way that may not make sense at first. I wanted to move the holes along the edge to the top and keep the mounting holes in the face. I created a rectangle the same size as the original, turned the original into a “hole” and centered both parts and grouped. Now I had the holes as objects with the correct dimensions without having to measure anything. It also trimmed off and kept the chamfers which was cool.
Next I had to remove the holes in the sides. Turning the part back into a solid, I added shapes that overlapped the holes I didn’t want, turned those shapes into holes and grouped. That left me with just the mounting holes and the chamfers. I turned the chamfers and mounting holes into holes, created a rectangle the same size as the original, aligned everything and grouped again. Now I have the original part without the holes along the side and a part that stuck out that I won’t need. Then t was a matter of placing holes where I wanted them for the threaded inserts. This whole process took less than 10 minutes.
Could I do this with Fusion? Probably. It would take me much longer because it brings both my PC and myself to our collective knees. I don’t “get” it and the PC can barely run it.
Apparently there must not be any programs because after all, one would have found them using Google. 
But seriously, could your question possibly be more vague? The question is akin to "Are there any hammers at the hardware store?’
Of course there are STP and STL editors. Perhaps you’ve heard of Bambu Studio? It lets you create a file, modify a file and then print it.
What are you trying to edit and for what purpose? Quality answers are derived from quality questions.
But to give you a head start. Here are the questions you need to ask yourself first before posting in a discussion forum?
- What am I trying to edit? Is it a geometric shape like a replacement part for my lawn more or is it a figurine for my Dungeons and Dragons set?
- What is my skill level at computer technology? Am I hopelessly lost using PowerPoint or I can make Visio sing like a church choir?
- Why am I trying to edit something and what? Is it because I have a model I want to print and I want to make major changes to it, or is it that I want to create things from scratch.
The answers to those question will help you determine your appetite for learning new software versus just tinkering.
my bambu studio is not sophisticated enough to perform the edits i want to and i cant get my solid egde to open the stl files i download
Well I think there are many tools outside which can do it but however as with program codes you are may in copyright matters so a lot to read before changing one single dote on or making a copy of a drawing like touching program source codes. The 3D printed part will than may belong to the Patent matter if it is covered by …. “May” because I`m not an expert on. And by the way, since I’m not an expert on I do not give a permission to anyone to distribute anything what I did on my risk… like music, which then finally ended in an absolute jungle of paragraphs and one lawsuits after the other.