Manager Gary Mills welcomed the 24-year-old back into the Minstermen fold on Tuesday following a three-month lay-off with a knee ligament injury.
Although Mackin will not be rushed into a senior recall, Mills was delighted to see the former Wrexham man take a significant step towards full fitness.
“Levi joined in with us for the first time on Tuesday, which is good news,” said Mills.
“We want to get him back and we will work hard with him now, and bring him along as best we can.
“We want to get him back to a good fitness level, and it was nice to see him back on the training field.
“It’s horrible when you are out for a long time and you’re not together with the other players. You are training on your own and at different times.
“There’s nothing like being out training with the rest of the players and getting on with what you want to do.”
With Mackin following fellow knee injury victim Chris Carruthers along the road to recovery, only striker George Purcell is left on the treatment list with his ankle problem.
Carruthers featured for the final nine minutes of the FA Cup first round win at Kidderminster on October 23 and made a 66th-minute appearance as a substitute at Forest Green last Saturday.
Said Mills: “He’s come back and taken part in the last couple of games. It’s nice to have him back.
“Touch wood, we have now got a virtually fit squad.”