You can use Affinity Designer grouping to make life so much easier, to define particular sets of layers of interest, use with symbols and much more.
You can select some paths either on the art board or via the layers panel and right click and select the group command OR use the layer menu and the first command there or just click the button in the top left corner. There are probably a few other options
You can select the container and duplicate it by holding down the alt / option key and you can modify the children within that container via the layers panel. You can move them back and forth between those containers, however many copies you generate. You can also duplicate using the edit menu and duplicate command
You can also add adjustment layers to the container as well as the children individual as well as to the container of the container (it can get complex). If you have selected the container and you go to the layer menu and new adjustment layer, the adjustment will only be applied to that container / children and not to any of the others. So if it is a black and white say, only that selected set will have the adjustment layer and only that will be turned into black and white.
You can select any object, the container or children or containers of containers etc and you can then move them to a new container, they do not have to be frozen in the one they were first created in. You can move them up and down the order in the panel. Also, if the container has a blending mode of difference etc or effects added (such as 3D) then that is not carried over with the path being moved. If it is moved into a new container with 3D / shadows etc it will then give the appearance of having that as well.
The entire container can be scaled and rotated etc and all the designs contained will also be resized and rotated as well. You can select the individual items and use tools such as the node tool to manipulate the nodes of any of the curves
You can also change the blending mode of the container as well as the individual children / curves. The children contained will not change if the blending mode of the container changes, however all the children will be changed visually. You can select the children and change the blending mode for those so you can have a container with difference and the children with linear light / color burn etc.
If you want to move a path out of a container or above or below another path, simply select and then drag above or below or drag the path out of the container and place it above the entire set or below the entry. The other paths in that will be untouched.
If you want all the items in a selected set to be added as a single symbol then you will have to collect them altogether in a container / child relationship and the symbol will be the container and all the items will be turned into a single symbol. If you don't set up a relation and just select a number of items and then turn those into symbols, you will just end up with lots of symbols all having one path.
There is also a paste inside that collects everything together in a similar way, when you use that command and have all the paths within the parent, the functionality is quite different and how it clips the paths is certainly different. The application has similar looking features with art boards and symbols etc