I'm not sure if you are suggesting this based on an actual experience you have with the mail adapter.
If you look carefully in the screenshot, the attachment name does not come nicely in the ASMA/DC fields. It is part of the value that actually is the MIME Content Disposition field of the email. So, yes, while it is possible to add DynamicConfigurationBean in the module chain, it will assign the full MIME field value (i.e. attachment, filename="Train_SG.txt") to the DC field that can be used in a Context Object.
Whether this will work using Condition Editor in RD will require some trial and error because MIME field values are sometimes inconsistent, therefore a little tricky. If that doesn't work, then it might be easier to extract the attachment name value in a UDF instead.