The conditions of ordering a suspended sentence in Switzerland is regulated by art. 42 of the Penal Code, in particular al. 1 and 2:
The court shall normally suspend the execution of a monetary penalty or a custodial sentence of no more than two years unless an unsuspended sentence appears to be necessary in order to prevent the offender from committing further felonies or misdemeanours.
If the offender received a suspended or unsuspended custodial sentence of more than six months within the five years prior to the offence, the sentence may only be suspended where the circumstances are especially favourable.
Entered into force from 2007, the first alinea makes suspension of serious penalties the rule rather than the exception, unless the court is convinced that the offender is likely to reoffend after making a prognosis regarding their future behaviour. An unfavourable prognosis (due to likelihood or high uncertainty of new offences) is required and the benefit of the doubt is given to the offender in accordance with general criminal law principles (BGE 134 IV 1).
For the application of al. 2, where the presumption of favourable prognosis is reversed, only a serious previous pronounced sentence prior to the commission of an offence is a disqualifying factor (especially favourable circumstances aside). The judge consequently cannot automatically disqualify the convicted from a suspended sentence because of a subsequent offence.
However, the judge has a large latitude and discretion in determining the prognosis and may take into account all circumstances related to the offender until the moment of sentencing, unless otherwise prohibited by law (e.g. offences erased from the criminal record can no longer be used against an accused).
The presumption of innocence should only apply in so far that the judge does not consider the accused guilty of the other offence, but relevant evidences may still be introduced to show the accused's behaviour and character.
While I cannot find a statement directly related to the determination of suspended sentences from decisions in French, the Federal Court had ruled pending criminal procedures may be used in the justification of preventive detention, if the accused is storngly suspected, bordering on certainty, in the other procedure (BGE 146 IV 326, para. 3.1 citing BGE 143 IV 9, para. 2.3.1). I do not know if the determination of the possibility of suspended sentences necessarily requires such a high bar, but it demonstrates the possibility of using pending offences for risk determination in criminal law context.
I will note another consideration that may be relevant, depending on the timing of the commission of a subsequent offence.
Swiss law provides limitations on concurrent sentencing with art. 49 of the Penal Code, in particular
1 If the offender, by committing one or more offences, has fulfilled the requirements for two or more penalties of the same form, the court shall impose the sentence for the most serious offence at an appropriately increased level. It may not, however, increase the maximum level of the sentence by more than half, and it is bound by the statutory maximum for that form of penalty.
2 If the court must pass sentence on an offence that the offender committed before he was sentenced for a different offence, it shall determine the supplementary penalty so that the offender is not more severely punished than he would have been had the sentences been imposed at the same time.
Only the most serious offence will become the base of sentencing if two or more sentences of the same form are appropriate for one or more offences. The less serious offences are only punished via an appropriate increase in the sentence for the most serious offence.
A subsequent offence committed before the sentencing of the first offence is eligible for the application of al. 2. An offence committed after the sentencing of the first offence is not considered as concurrent but independently sentenced. This is a relatively new change in jurisprudence (without statutory change by Parliament) by the Federal Court in 2019 to prevent undue advantage for a serial offender.
Note that suspension is not considered as a form of penalty, but only a way to execute the penalty. The appropriate penalty is always first determined, then the possibility of suspension considered.