Is an appeal admissible against the decision refusing suspensive effect in the complaint proceedings?
No. The grant, refusal, or withdrawal of suspensive effect is a purely procedural measure, and neither the LP nor cantonal procedure provides for an appeal against such a decision.
The complaint/supervisory appeal may only target measures or decisions of debt-collection bodies. Refusal of suspensive effect is not an enforcement measure but a procedural ruling; therefore no statutory remedy exists under federal or cantonal debt-enforcement law.