In the game I want to make, there will be many similar objects (such as creatures or clothes). It seems to me that it is very difficult to make them from scratch every time (since any innovation will require making changes to each of the objects). Can this be done more conveniently? Perhaps there is a way to standardize these objects?
There are a couple of features you can use for this. One way is to use behaviors. You can make your own custom behaviors too. That way, you can write your logic once, then add the behavior to all the objects you want to use that same logic. It’s a little complicated to use, but check out the wiki page on it: http://wiki.compilgames.net/doku.php/gdevelop5/behaviors/events-based-behaviors
Another way, that is a lot simpler, is to use object groups. Open the group object window with the icon with three cubes on it, usually in the top right. Create a new group, and add objects to it. After that, you can refer to that group in your events instead of specific objects. The conditions or actions will apply to all of the objects you put in the group.
One extra note:
One thing I have struggled with is having multiple instances of the same object in events. The way it works is that as soon as you mention an object in a condition, from that point on all other conditions and actions that mention that same object will only apply to the instances that satisfied the condition. Trouble is, its difficult to check the other instances of the same object. I really have problems with checking if instances of objects collide with other instances of the same object, for example.
The reason I mention this is that when you reference groups, it means all of those instances of all objects in the group are affected in this way.
So, I suggest working on small projects to start with, to learn the rest of gdevelop. Once you are ready for larger projects, you can try out groups or behaviors, but even then its often better to stick to one instance per object type if you can, even if its a little tedious.
Of course, when it gets too tedious with too many instances these things can still help out a lot. But be prepared for some troubleshooting since you will get some strange results and have to work around them.