While currently not functional for me, RDKit's cookbook includes a relevant entry to this, though. Instead of dashes, the dative bond would be represented by an arrow pointing toward the transition metal, e.g.
(from RDKit's Cookbook)
in a section called Organometallics with Dative Bonds.
If you use
.sdf in the v3000 format,* RDKit may be adjusted to visualize dative bonds as dotted lines, too:
(Esben Jannik Bjerrum, cheminformania.com)
*) The current definition of
.sdf files by Biovia (August 2020, link to .pdf) describes in detail the types of bonds available in the v3000 format to the bond block (cf. p. 11). Type
9 is set for coordination with dipolar bonds of either sub-type
COORD for coordination bonds in metal complexes, or
DATIVE for bond between Lewis acids and bases. (There might be a concptual overlap here.) Bond type
10, by the way, offers two sub-types to handle hydrogen bonds, too.