Can multiple adjustments (via the Demand Adjustment calculation option) be applied to the demand at a junction?

Yes. All adjustments related to the demand at a junction will be applied to it.
An example of this is shown below.

What order are the adjustments applied in?

The demand adjustments in the calculation options are applied first, in the order they are displayed. The order can be edited with the arrow icons.

After the demand adjustments from calculation options have been applied, then the demand pattern multiplier is applied.

For example, take a look at the following demand and adjustments.

Junction J-1 is included in all demand adjustment scopes listed above.

Row 1: 100*1.5=150
Row 2: 150*0.8=120
Row 3: 120+10=130
"Demand Pattern A" multiplier at current time step = 2
Adjusted Demand: 130*2=260

Does it matter what order the adjustments are listed in the Calculation Options dialog?

When all adjustments have the multiply operation then the order is arbitrary because of the associative property. However, as shown below, changing the adjustment order can change the resulting demand if there are operations used such as add.

Row 1: 100+10=110
Row 2: 110*1.5=165
Row 3: 165*0.8=132
"Demand Pattern A" multiplier at current time step = 2
Adjusted Demand: 132*2 = 264

What if a junction has two pattern multipliers applied?

Each base demand will have the demand adjustments in the calculation options dialog applied (in order). Each of those adjusted base demands will have their respective pattern multiplier applied. Those adjusted demands are summed. The example below assumes that the calculation options adjustment order matches the first example above (add operation last).

Row 1: 100*1.5=150
Row 2: 150*0.8=120
Row 3: 120+10=130
"Demand Pattern A" multiplier adjustment at current time step: 130*2=260

Row 1: 80*1.5=120
Row 2: 120*0.8=96
Row 3: 96+10=106
"Demand Pattern B" multiplier adjustment at current time step: 106*0.5=53

Adjusted demand at junction J-1 at current time step: 260 + 53 = 313

See Also

Forum: How does Watergems CONNECT Edition handle multiple demand adjustments (via Calculator Options) applied to the same element?
Wiki: Calculated demand does not match entered demand
Wiki: How to edit demands, unit demands, or a subset of demands globally
Wiki: Importing Demands From A Spreadsheet