Is there a way to generate SMILES from ChemDraw files?
Of course openbabel can do this (at least with release 3.1.0 from here).  To rewrite a file here and then, the GUI on top of the program on top may suffice for you.  However, you would skip a lot of the program's functionality if not trying to interact from the command line: for one, the conversion basically follows the pattern of
obabel -icdx input.cdx -osmi -O output.smi

which actually may be faster than clicking in an interface. For the other, that openbabel offers multiple interfaces to automate file transformations programmatically, i.e. to interact with programming languages like Python and C.  See the current  documentation rather than the a bit outdated on the project's senior page.
Note 1: ChemDraw offers a structure to SMILES string conversion, too.  Be aware that a .cdx file may contain much more information, than a SMILES string may retain.  Seeking for a text-only representation of the molecular structure, axial chirality (P/M) is an example where a SMILES string is less suitable than, for example, an InChI string.
Note 2: Openbabel aims to interconvert chemical formats; on occasion with a visual output like .svg, or .png.  RDKit has a stronger emphasis on computing with the molecules (a.k.a. cheminformatics) as required while interacting e.g., with large sets of data and databases.  There is some overlap of the two programs, and «the trick» is rather to recognize where the two are complementary to each other.