|Oliver von Spreckelsen|
First Hollow's Last Hope
then Crown of the Kobold King
then the Pallid Plague
then the Return of the Kobold King
then Carnival of Tears
and conclude with Hungry are the Dead
There are many small things you can do to knit those adventures together to form a cohesive campaign.
Make Hollin appear in the queue before Roots & Remedies and then Hollin thanks the PC's for rescuing his sister by giving them a carved little figurine in their likeness. Some days afterwards Ralla comes to the PCs that Hollin is missing... instant connection and identification. If you also include Ralla's "Chef" after she informs the PC's that her brother is missing to bring her back to work it also introduces one of the movers and shakers in Falcon's Hollow...
To continue the campaign you can also integrate the Society scenario The Pallid Plague from Season 1? Scenario #43. This guys were also responsible for the "poisoning" Brookman's Well that led to the events of HLH. You can let the PCs find a symbol of Urgathoa in the trees nearby when they investigate the well at the start of HLH.
The biggest change you need to make is to foreshadow the main villain of the campaign by including the group in HatD in the group (or the remains of the group) that you encounter in CotKK. The two groups became separated when the tunnel between the different dungeon levels collapsed (i.e. the group around the main villain did that and left the others behind "to guard the entrance" those have been overwhelmed by the kobolds.
You have one challenge in CoKK and that is the kissing monster. In order to have a scroll of rRemove Disease" nearby, the vistim that is with the ghouls has been the party cleric and in his satchel the PCs can find the scroll. Edgrin knows about that.
The events about Namdrin Quinn and the fey attack can be foreshadowed in The Pallid Plague and there is a random encounter, where a dead fey can be found in the woods. Use these to set the mood for the conflict with the fey.