Which trains aren't showing up? The Freccia or the regional? The fast one should I think be all posted. Like I tried to state earlier the regional won't go up in price. So if you see the Freccia at a price you like buy it now and buy the regional when it's posted.

Traveler Nick, it's the 4 Freccias between 11:00 and 12:00 that aren't showing on August 20th. It seems unusual that they'd cut the schedule back that much from what they're showing during the month of May.

Mestre to Milano central? Italo is only showing up to the beginning of August. Just wait. . Things will likely be fine in a week or two.

Yeah, https://www.trustpilot.com/review/www.trenitalia.com ratings of Trenitalia are scary low, you're better off using italotreno

Trenitalia shows for August 20th the Freccierosse
Mestre dp 11.02, 11.32, 12.02
The regionali Mestre dp 11.24 - Verona ar 12.39 and Verona dp 12.45 - Milano C ar 14.35 are not yet shown
Italo may have a train at 12.13

Thanks everyone for your input. I went ahead and booked the Freccias only for Mestre > Milan and Milan > Santa Lucia. I'll book the regionales to/from Como when they become available online.